The Darkness Within
by Nutella Swirl
Summary: Everyone has a dark side, whether they know it or not. It can destroy a person, and that's what's happening to Leo. If his family doesn't figure out why Leo's acting different and help him overcome the darkness within him, Leo's good side will be lost forever.
1. Gone

**A/N: This story takes place after Leo is fully healed in season 3 (2012 version).  
><strong>

**Also, I don't own TMNT.**

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><p>It had been nearly six months after they had escaped New York City and fled to April's family's old farmhouse. Nearly six months after the Kraang invasion. Nearly six months after Leo crashing through the window.<p>

Nearly six months without Master Splinter.

Leo sighed, staring outside the window. It was drizzling. The rain drops scattered around the grass and plants, leaving little droplets of water everywhere.

Leo loved the rain. He would go topside, sitting on an abandoned rooftop, gazing down at the scene below. It was usually peaceful, since no one really went out in the rain, and Leo liked it that way. The rain was his escape from reality, from his problems, from his family. It would be just him and the rain.

The rain reminded him of being alone, which reminded him of his family, which remind him of Master Splinter.

Master Splinter, Leo's father and sensei, was... gone.

No one even knew if he was still alive. The others had seen the Shredder fight him and push him into a whirlpool, and then he was gone.

Leo desperately wanted to his father's face again. He wanted to tell him one last thing.

That he loved him.

Leo diverted his gaze away from the window and looked at his brothers and April and Casey. They were all watching something on television, and Mikey seemed to be enjoying it the most.

_What are we doing here?_ Leo wondered. He was fully healed now, and he and the others were just lounging around when there was trouble going on. No one had any idea if the Kraang were still invading Earth. They would have to find out.

It was time to return to New York City.

It was time to put and end to the Kraang, to save the city, to find Master Splinter, dead or alive. Leo hoped it was the latter, like everyone else, but there was no telling if he was still alive.

Leo shook the thought away from his head. It wouldn't help to think about his father not being alive.

He walked over to the others. "Guys, it's time to go back."

Everyone looked up, except for Mikey.

"Where?" asked Casey.

"To Hawaii." Raph rolled his eyes. "To New York City, duh!"

"It's about time we went back there," Donnie commented. "We still don't know what happened to Master Splinter and the other people in NYC."

April slowly nodded. "Yeah. Let's go."

Mikey retrieved Ice Cream Kitty from the freezer and put her in a cooler. The others got food and other items they would need. Then they all piled up into the Party Wagon.

Casey was driving with April right next to him. Directly behind her was Leo, and next to him was Donnie. In the back were Raph and Mikey.

April was staring out the window, not saying anything. Leo did the same, not knowing that he did so seconds after April did.

"Ooh, look, Leo's a copycat!" Mikey said as he noticed this.

"Am not," Leo replied, still looking out the window.

"Oh yeah? Then why did you start staring out the window when April did? Huh?" Mikey asked.

Leo said nothing.

Mikey frowned, but didn't say anything either. If Leo was going to ignore him, he'd just do the same.

It stopped raining outside, but there were still rain drops on the van's windows. Leo closed his eyes and let his finger make a little drawing on the window next to him. When he opened his eyes, he saw that he had drawn a person crying.

_Weird_, he thought to himself.

A few minutes later, Casey announced, "We're there!" The turtles looked out the windows to find themselves in the familiar, bustling streets of New York City. The buildings that had been broken in the invasion were fixed, and none of the humans were mutated Kraang zombies.

"I wonder where my dad is," April said aloud.

"Don't worry, April, I'm sure we'll find him soon. When we do, I'll give him the retromutagen," Donnie said, trying to comfort her.

April gave him a small smile. "Thanks."

Casey parked by an abandoned building. Everyone climbed out of the Party Wagon and went down into the sewers.

"First things first. Let's look for Master Splinter," Leo said.

"You know he might not be alive anymore," Raph said. He was trying not to cry, so his words came out slowly.

"I know, Raph, but we still have to find him," Leo replied. They were about to split up to look for Master Splinter when April stopped them.

"I sense him; he's that way," April said, pointing to the right. The others followed her into a tunnel which ended in a small, room-like place.

And in the center was none other than Master Splinter.

He was lying down, his stomach on the ground. One of his arms was next to him, the other above his head. His eyes and mouth were shut.

They didn't need to try to find a pulse to know that he was dead.

Mikey was the only one who spoke. "NOOOOO!" he shrieked, crying into Donnie's plastron.

Everyone else was crying. Even Raph, the strongest turtle, couldn't hold his tears back.

"Father," Leo whispered as he stroked his father's face. Somehow he couldn't cry, but he could feel the pain in his heart anyway.

He hadn't deserved a death like that.

He was too much of a good person to die like that. He had never, _ever_ done anything wrong.

Leo wanted to cry, to let all those tears out, but somehow they didn't come. They refused to spill, staying inside of Leo's body.

And then he heard a voice. It was so faint that it might have just been his imagination, but he was sure it wasn't.

_"I got my revenge on your father. Now I shall get my revenge on you."_

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><p><strong>AN: At first I was going to make this a one-shot (the one-shot would be the next chapter), but then I decided to turn this into a chapter story.  
><strong>

**Please review, follow, and favorite! :)**


	2. The Note

**A/N: I don't own TMNT.**

**If you were wondering how April sensed Master Splinter even though he wasn't alive, it's because she sensed his spirit.**

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><p>It had been a week since Master Splinter's funeral. They had moved into the lair after that.<p>

They were all slowly getting over his death. Mikey tried to cheer everyone up instead of grieving. Raph was mostly punching away at the practice dummy or hanging out with Casey. Donnie was tinkering in his lab, fixing up the things that had gotten broken in the lair from the invasion. He was also trying to figure out where April's dad and Casey's family could be.

Leo was fairly quiet, only speaking when he had to. He distracted himself by watching Space Heroes episodes, but he still couldn't get his mind off of Master Splinter and the voice.

_"I got my revenge on your father. Now I shall get my revenge on you."_

It was undoubtedly the Shredder. But how Leo could hear it or how the Shredder would get his revenge were things he didn't know.

"Found it!" Donnie said triumphantly from his lab, cutting off Leo's thoughts.

"Found what?" Leo asked as he entered the lab.

"Found the place where April's dad might be," Donnie replied. "Apparently, the Kraang changed TCRI to IRCT."

Leo raised an eyebrow. "IRCT?"

"Yeah. It's TCRI backwards. They probably changed it so the police wouldn't get them, even though it's still obvious," Donnie explained. "I hacked into their system, and it says that they've been keeping the Kraang zombies." He nodded towards the computer screen.

Leo looked over Donnie's shoulder and read the information. "Hmm... we'd better go in there, then."

"Yeah. I'll get my retromutagen and everything we might need," Donnie said as he started gathering the retromutagen, smoke bombs, and other stuff. Leo told the others everything and they got ready.

April was coming along, too. It was her dad, after all. Her powers would be helpful, too, in finding where her dad was.

Once they were ready, they all went topside and quietly sneaked towards the TCRI building, which now said IRCT.

Donnie located the least guarded window and quietly opened it. He slipped inside, motioning for the others to follow him.

Some of the Kraang in their robotic bodies were there, but were quickly taken down.

Donnie led them though a dimly lit corridor and into a huge room filled with Kraang zombies.

"How do we know which one is April's dad?" Mikey asked.

He was answered with April's whisper and gesture to follow her as she used her power to track him. "This way."

The turtles and Casey follow her, tiptoeing in the shadows. They finally reached April's dad, who was walking towards one of the Kraang.

"...and make sure that they never return," the Kraang was saying.

April's dad said robotically, "Yes... They will never return..."

"Now!" Leo whispered to Don.

Donnie took one of the containers of retromutagen he'd brought and spilled it over April's dad. He froze as the retromutagen seeped in through his clothes and touched his body.

"It's working!" April whispered.

She was right. The pinkish tinge disappeared. A few seconds passed, and Mr. O'Neil, human and whole, was standing right before them.

"Dad!" April cried, running into her father's arms.

Mr. O'Neil blinked, then looked down. "April?"

They hugged, but no one noticed the Kraang behind them.

"The ones known as the turtles have returned," one of the Kraang said.

April pulled away from her dad and turned around. "Oh no."

"Don't worry, April, we'll take care of them," Donnie said as he pulled out his bo staff. The others took out their weapons.

"Alright! An all you can beat buffet!" Raph said, taking down the Kraang closest to him.

The rest was a blur as the ninjas and Casey took down Kraang after Kraang until only the Kraang zombies remained. Donnie had brought lots of retromutagen, luckily, and poured it over all the mutants. Among them were Casey's dad and sister, and they had a small family reunion.

"Wanna go on a patrol?" Raph asked as they all came out of the IRCT building and headed to the rooftops. April, Casey, and their families had left to their homes after good-byes.

"Sure," Leo said. "We haven't been here for six months, so there might be some crimes going on."

They went on a patrol, checking out nearly all of New York City. They didn't find anything and were about to go back to the lair when they heard a Purple Dragon.

"Just give us the money!" he hissed to an elderly man. The old man refused and got beaten up, his head hitting against the walls of an alley, knocking him out.

The Purple Dragon dug though the man's pockets and took out a wallet. He showed it to his friends, grinning.

The turtles interfered then. The Purple Dragons were attacked by seemingly invisible creatures before they also fell, unconscious.

Leo took the wallet which had fallen during the fight and placed it in the old man's pocket. He seemed to be waking up.

The turtles were about to leave when a piece of paper flew down from the sky and fell onto Leo's head. Leo frowned, took it off his head, and read it.

_Just how many times have you wanted to cry but couldn't shed even a single tear?_

Leo stared at the note, his hands shaking. His face paled and his legs wobbled.

"Leo? You okay?" Raph asked, noticing the sudden change in his older brother.

Leo quickly resumed his Fearless Leader mode and slipped the note in his belt. "Yeah, I'm fine. Let's go home."

Little did he know that this was all connected, and not just a coincidence.


	3. The Voice

**I don't own TMNT.**

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><p>Darkness.<p>

There was only darkness; not even a single bit of light was to be seen. He could even_ feel_ and _see_ the darkness, no matter how crazy it seemed.

He racked his brain; trying to remember how he got here. The last thing he could remember was going into bed.

"So I either forgot how I got here or I'm in a dream," he mused out loud.

"That is right, Leonardo," a deep and dark voice said.

Leo turned around and paled at what he saw in the midst of the darkness. "_Shredder_? But- how-"

"Now is not the time, Leonardo," the Shredder said. "I am just here to let you know that my revenge on you has already started. Have you seen the signs?"

Leo paled even more. "You mean the note was a sign? And your voice I heard, too?"

"Yes," the Shredder answered. "I am here to let you know that my revenge has started already. Soon, you will not know yourself and become lost. And when that happens, you will come under _my_ power!"

"What?! _No!_ I won't let it happen!" Leo said.

"You will, Leonardo," the Shredder said, smirking. "And there is no way you will be able to stop it."

With that, the Shredder disappeared. The darkness around Leo disappeared, and he was in his own bed.

Leo took out the note and unfolded it, reading it again. He could feel his legs wobbling again even though he was lying down.

_Why do my legs feel like jelly? It's just a stupid note, and that was just a dream,_ he thought to himself.

Yet somehow he knew that the Shredder had been telling the truth. He didn't get how the Shredder would get Leo under his power, though. But if he did, the things the Shredder would probably make Leo do were unimaginable...

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><p>"Are ya gonna finish up your breakfast, Leo, or ya just gonna sit there starin' at the wall?" Raph asked.<p>

Leo snapped back to reality and saw his half-eaten cereal. He sighed. "Sorry, Raph."

"There's no need to be sorry," Raph said gruffly. Then, in his normal voice, he asked, "Are you okay, Leo? You've been acting kind of... strange... lately."

"Of course I'm fine," Leo said, sending Raph a reassuring smile. "Why wouldn't I be?"

"Just checking," Raph said. He saw the time and said, "Well, I better go train in the dojo now. See ya later."

Leo stared at Raph going off to the dojo and sighed again, letting his fake smile disappear. _If only you knew... but I can't let you guys worry._

He looked back at his unappetizing, soggy cereal._ Why even bother eating when I'm not even hungry anymore?_

_Why should I even believe the Shredder? He's just some unreliable villain, and he killed Master Splinter!_

_Master Splinter..._

_If only he were here now. Then I could tell him everything and he would know what to think._

Leo sighed again. _But I'm on my own now..._

"Hey, Leo, wanna listen to some jokes?" Mikey asked, holding up a joke book. He had been noticing that his family was feeling down, probably because of their fathers' death. It was his job to keep the family happy and smiling.

"Sure," Leo answered absently. His mind was somewhere else, though, and he didn't notice that Mikey was trying to get him to answer the joke until he said, "LEOOOOO!"

"What?" Leo asked, snapping out of his thoughts.

"When is the best time to eat a banana?" Mikey read.

"I don't know," Leo said. Inside, he was thinking, _And I don't really care either._

"After you peel it! Get it? Huh? Do you get it?"

"Yeah. I have to go now, Mikey, okay?" Leo said.

Mikey's face fell, but he just said, "Okay."

Leo got out of the room as fast as he could. It wasn't that he didn't like Mikey's jokes; he just didn't want to answer them now.

_"Good, I see that you are listening to me,"_ the Shredder said from inside of Leo's head.

"What? How can I hear you when you're not even here?" Leo asked, perplexed. He was in his own room now, so there was no danger of his brothers hearing him.

_"Because you are almost under my control,"_ the Shredder said. _"I see that you left Michelangelo. Good!"_

"I didn't listen to you! I left because I didn't want to listen to Mikey's jokes!"

_"Oh, stop lying! You listened to me!"_

"SHUT UP!"

The door flung open and Raph, Donnie, and Mikey entered.

"Uh, Leo, are you okay? We heard you talking," Donnie said.

"I'm _fine_," Leo answered. _What's up with everyone asking me if I'm okay lately?_

"Are you sure? Raph said you were acting weird lately-" _Thanks, Raph._ "-and Mikey has his suspicions, too," Donnie continued. "Let me check your forehead- God, you're burning up! Raph, Mikey, go get some cloths and soak them in cool water!"

"I'm _fine_, Donnie!" Leo said again.

"You are _not_," Donnie said. "You have a fever. Maybe that's why you've been acting like that."

"Let me go!"

"Leo, you're sick! You can't go until you get better!" Donnie said, holding Leo down firmly.

Leo struggled out of Donnie's grasp and failed. _Since when was Donnie_ this_ strong?_

Raph and Mikey returned with some cloths. Donnie put on on top of Leo's head. It felt good to Leo. _Maybe I really _am _sick..._

"You could be delirious, too," Donnie said. "You were talking to someone who wasn't even there. So I'm going to have to make you stay here with someone with you at all times."

Leo groaned inwardly but said, "Fine."

After a small discussion that Leo didn't pay attention to, Raph and Donnie left, leaving Leo with Mikey. Mikey started reading a book to his older brother, but Leo wasn't paying attention.

_"I made you have this fever," _the Shredder said inside of Leo's head, _"so your brothers don't suspect anything. Smart, huh?"_

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><p><strong>AN: Dun dun dun! Suspense! :P  
><strong>

**I actually thought of this chapter while writing it so it might not be as good as the others... the next chapter will be better though, since I already thought of it!**

**Remember to review, follow, and favorite! ;)**


	4. Mutation Day

**A/N: I meant to post this earlier but I didn't have the time, sorry about that! **

**Also, I renamed the title and summary because I didn't like the old ones. So, if you were wondering, yes, this is still the story "Hidden Emotions" except now it's called "The Darkness Within."**

**I don't own TMNT.**

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><p>It turned out that Leo not only had a fever, but also a stuffy nose, sore throat, the coughs, and lots of headaches. He was confined to his room for two whole weeks until Donnie said that he was better. Being stuck in his room sucked, especially since someone had to be with him at all times.<p>

Leo was forced to close his eyes as his brothers dragged him out of him room, claiming that there was some kind of surprise. When he was finally allowed to open his eyes, he was amazed.

Raph, Donnie, and Mikey (Mikey claimed that he did most of it, though) had decorated the whole lair with blue, red, orange, and purple streamers. There were balloons and confetti in the same colors. In the middle of the living room was a banner that read "Happy Mutation Day!"

"Happy Mutation Day!" Mikey said, dropping a handful of blue confetti over Leo's head.

"Wow, guys, this is amazing!" Leo turned around and smiled at his brothers. He didn't understand how he had forgotten that it was Mutation Day, but at the same time, he couldn't believe it either. Had it really been a whole year since they had first gone topside?

"Glad you think so," Donnie said. "And this isn't it, either. We're going to have tons of-"

"Got the pizza!" Mikey informed his brothers. He had zipped out of the room to gather ten boxes of pizza, all stacked on top of each other. He held them on one hand as if he was a waiter. The boxes shook and wobbled until they fell.

"Oops." Mikey started picking up the boxes, this time placing them on the dining table.

"As I was saying, we're going to have tons of pizza. And April's going to bring a-" Donnie was cut of again as the said human entered the lair.

"Hey, guys! I brought the cake!" April greeted. She set the cake next to the pizza boxes on the table. The cake had white frosting with swirls of red, orange, blue, and purple icing. The words "Happy Mutation Day!" were written with green icing.

"As I was saying," Donnie continued, "April brought the cake. So now we're going to celebrate!"

"Nice rhyme, dude!" Mikey said.

Raph rolled his eyes. "_Cake_ and _celebrate_ don't even rhyme, Mikey."

"Who cares?" Mikey said, stuffing a slice of pizza in his mouth. Everyone else got their own slices and began to eat. Casey came in the middle and joined them, and so it was the family of mutants and humans celebrating Mutation Day.

After all the pizza slices had been finished, the cake was cut and served. Mikey had somehow managed to eat three boxes of pizza and four slices of cake without feeling sick at all.

It was during his second slice of cake when Leo's head began to throb in pain. He stopped eating and clutched his head.

Donnie noticed this and asked, "Leo, are you okay?" But Leo didn't hear him. All he heard was the Shredder in his head again.

_"It is about time you attacked your brothers,"_ the Shredder said.

_I will never hurt my brothers!_ Leo thought.

_"Yes, you will! Do you know who you are talking to?"_

_You're the Shredder... and you can hear my thoughts?!_

_"No, I am not the Shredder, and yes, I can hear your thoughts."_

_Then _who_ are you?_

_"I am your dark side. I am in the Shredder's form, so that's why I sound like him. The Shredder ordered me to make you evil for his revenge,"_ the Dark Side said.

_My Dark Side? You mean... dark sides are real?_

_"Yes. And now I will make you evil! There is no way you will be able to stop me unless you fight me, but you are too weak!" _the Dark Side said, laughing evilly.

Leo didn't have time to respond when the pain in his head spread throughout his body. He tried to fight it, but it was too powerful.

_"You are too weak!"_ the Dark Side said. It was the last thing Leo remembered hearing before his mind went numb and fell into darkness.

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><p>The Dark Side of Leo, Dark Leo, emerged from his hiding place inside of Leo. He took over the good Leo's body, but no one else realized it. Leo's sapphire eyes turned bloody red.<p>

Dark Leo reached for one of Leo's katanas as swiftly as he could and turned towards the turtle next to him. It was Raphael.

Dark Leo plunged the sword into the Raph's shoulder. Raph, who hadn't expected Leo to attack him, gasped out in pain as waves of blood trickled out of his new injury.

Dark Leo looked over at the other turtles, pointing the katana at them. His lips formed into a smirk.

"Leo," Mikey said. "You have to listen to me-"

Upon hearing his name, the good Leo woke up. The pain returned, but a newly found strength fought against it until it disappeared.

Leo took over his body again, his eyes turning back to their normal shade of blue. He stared his katana covered with blood and gasped. "No," he whispered. The world around him spun. His eyes rolled back into his head and he fainted.

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><p><strong>AN: This chapter is a little short, but I wanted it to end here. **

**Well, now you have an idea of what's going on...**

**My next update might come in a couple of weeks because of winter break since I'm going to see some relatives. I'll try to update, no guarantees though. **

**Remember to review, follow, and favorite! c:**


	5. Red Eyes

Leo's eyes finally fluttered open a few hours later. He was on his bed in his room.

His memory came flying back at him. Raph... Raph was hurt!

He could hear voices outside of his room. With a little effort, he was able to make out the words.

"When's he gonna wake up?" That was Raph.

"I. Don't. Know!" Donnie sounded annoyed, as if he had answered the question over and over again.

"Let's go check on him now," Mikey said.

Leo quickly closed his eyes and tried to make himself look like he was still out.

The door opened and Leo's brothers entered.

"He's still out," Raph said unhappily.

"I don't think so!" Mikey walked over to Leo and tickled him. Leo tried hard not to laugh or open his eyes but failed.

"Okay, okay, Mikey, I'm awake." Leo sat up and gently pushed Mikey away from him.

Donnie and Raph, who were about to exit the room, turned around upon hearing Leo's voice.

"Leo! You're awake!" Donnie went over to Leo and check over him. "Hmm... breathing's okay... no major injuries..." he was talking mostly to himself.

Leo looked up at Raph and wished he hadn't. Raph's shoulder was covered with a slightly reddish bandage. Walking seemed to hurt him, but he tried not to show it. But he couldn't hide it from Leo.

Leo swallowed and looked away.

He had failed.

_Again._

Mikey left the room to cook some food for Leo. Donnie left, too, after checking over Leo, leaving Raph and Leo alone.

"Leo," Raph began.

Leo refused to look up at his immediate younger brother and stared at the floor.

"I'm not mad."

Leo looked up in confusion. _Raph _wasn't_ mad?_

"Look, bro, I just want to know why."

Leo looked down again and stayed silent. It was that way for a couple of minutes until Raph broke the silence.

"Something's wrong." It was more of a statement than a question.

"Look, Leo, I want to help. Something's bothering you and you need help."

"I don't need help," Leo finally said.

"Oh, so there _is_ something wrong," Raph said.

Leo didn't answer.

"I want to help, Leo. Is it really too much to ask for?"

No, it wasn't. Leo just didn't want his brothers to worry about him. He could handle this by himself.

Raph looked at Leo in the eye. "I just want you to know that we'll always be there for you." With that, Raph left the room.

Leo stared at the ceiling. It was nothing, really. Nothing _they_ had to worry about.

Still, he had failed.

He had failed. He had vowed to protect his brothers at all costs, yet now he had just hurt one of them.

Maybe he hadn't done it directly, but he had still failed.

He was a failure. Nothing but a failure.

If he had just listened to Donnie, everything would be fine.

But no. He had argued. Donnie got hurt, he himself got hurt, and Master Splinter...

Master Splinter was more than hurt.

Leo fell asleep with those thoughts swirling around in his head.

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><p>Leo woke up a few hours later. He glanced at his alarm clock. It was only 1:47 am.<p>

He smelled some food in his room. Looking around, he saw a plate of macaroni and cheese on the table. He was very hungry, so he finished it quickly even though it was cold.

He saw a folded piece of paper on the table, too. Leo unfolded it and it read,

_We're always here for you, bro._

Leo smiled, forgetting his thoughts from before. Yes, his brothers were always there for him. And he'd always be there for them, too.

_"That's what you think, huh?"_

Leo gritted his teeth as he was taken way from his room and pulled into darkness, silently cursing. _Why did it have to be_ now_?_

_Show yourself!_ Leo thought to his dark side.

A figure emerged from some black mist. The figure looked exactly like Leo, except he was black and had red, glowing eyes. _"You can call me Dark Leo,"_ he said.

Leo glared. _You and I do _not_ have the same name._

_"I'm sorry, but we do,"_ Dark Leo said, not looking very sorry. _"It's about time you hurt your other brother, Michelangelo."_

_No! Not Mikey!_

_"Sorry. Shredder's orders." _Dark Leo smirked as he took over Leo.

Leo gasped as pain spread throughout his body. He struggled against it, but he was too weak. Dark Leo took over him, but kept him conscious so Leo would know what he was doing.

Dark Leo silently crept to the dojo. Leo's brothers had hid his katanas there after what had happened to Raph. He got the weapons and was about to go out of the dojo when the lights flickered on.

Mikey was standing in the doorway. He had heard someone walking and wanted to check what it was, only to find it was Leo. "Leo? What are you doing?"

Dark Leo went over to Mikey and brought one of his swords down. Mikey quickly dodged and took out his nunchucks. "Woah, dude! Be careful!"

They began to fight. Mikey noticed that something was wrong with Leo. He wasn't fighting as good as he usually did. It was easy for Mikey to knock one of Leo's katanas out of his hand.

Dark Leo knew that he wasn't as good as fighting as Leo, but ignored that fact and glared at Mikey, preparing to attack again.

Mikey looked up into Leo's eyes and then he knew what was wrong.

Leo's eyes were red, just like the time when he had attacked Raph.

Dark Leo saw that Mikey was distracted and quickly pinned the orange masked turtle down. Mikey struggled out of his grasp but failed. He gasped when he saw the katana next to his neck.

At that moment, Leo used all of his strength to push Dark Leo away. His eyes turned blue again. He took control of his own body again and gasped when he saw the katana next to his little brother's neck. Leo quickly sheathed the sword and got off of Mikey.

"Mikey? Are you okay?" Leo asked.

Mikey nodded. "You should've seen your eyes! They were red!"

Leo froze. "They... what?"

"Your eyes were red," Mikey repeated. "C'mon, let's go back to bed."

They went back to bed, but Mikey's words were still stuck in Leo's head.

_Red? How were my eyes red?_

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><p><strong>AN: I think I'll be able to update next week but I'm not sure about the week after.  
><strong>

**Remember to review, follow, and favorite! I'll update faster if I get lots of reviews!**


	6. Space Heroes

**A/N: Meant to post this yesterday but I was sick. :/**

**I don't own TMNT.**

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><p>Raph glanced at his older brother sitting across from him, picking at his breakfast. He seemed to be fazed by something, but Raph didn't know what.<p>

Leo looked up at him and Raph quickly looked away, busying himself with the food. Leo looked back at his own food, sighing inwardly.

Raph took another peek at Leo and saw dark circles under his eyes. It was obvious that the turtle in blue hadn't had a good night's sleep, which wasn't very surprising, considering what had happened the day before.

Raph looked over at his wrapped up shoulder and cringed. It still hurt. He hadn't cringed because it hurt, though. It was because the person who had hurt him was his own brother.

His brother, the Fearless Leader, Splinter Jr., whatever Raph called him. But it was still Leonardo who had hurt him.

Raph looked at Leo again and asked, "You okay?"

Leo didn't answer at first, but after a few seconds Raph heard a mumbled response. "M'fine." He pushed his chair, got up, and walked away, his food forgotten.

Raph looked at his departing brother. Something was definitely wrong, but what?

_Maybe Donnie has answers,_ he thought. Raph quickly finished his breakfast and made his way towards Donnie's lab.

Donnie was upgrading the security system. He heard the door open and saw that it was Raph. "What needs to be fixed?" he asked out of habit. Raph was the turtle who broke most of the things in the lair.

"Nothing," Raph said.

"Nothing? Then why did you come in?"

"Well, it's because..." Raph stopped. He hadn't figured out how he would say this to Donnie, but it was too late to back out now.

"Because what?" Donnie asked, not very interested. He went back to upgrading the security system, only half listening to Raph's words.

"It's about Leo."

Donnie looked up from his computer screen. "Yeah?"

"Something's wrong about him. He isn't acting like himself. You know what happened yesterday."

Donnie looked over at Raph's shoulder. "Is it hurting?"

"No," Raph lied. "But aren't you going to figure out what's wrong with him?"

"Yeah, once I'm done with this."

"Why not now?"

Donnie sighed. There really was no reason why he couldn't check on Leo now. He was just... afraid. Not afraid _of_ his brother. He was afraid _for_ his brother. None of them knew what was wrong with him, which made it... creepier, kind of. Scary, definitely.

"I'll go." Donnie turned away from his computer and went to Leo's room. He knocked on the door, waiting for a response.

Leo opened the door and let Donnie inside. "Anything you need?"

"Uh, well, I just wanted to know if you were feeling fine," Donnie said, taking note of the sleepiness his eyes held.

"I'm fine, Donnie. Why do you guys keep asking that?" Leo said, clearly exasperated.

"Leo, you haven't been acting like yourself. What's up?" Donnie asked in a stern, you-better-tell-the-truth voice.

"The ceiling." Seeing Donnie's frown, Leo sighed. "I'm just tired!"

Donnie stored that in his mind. "And what else?"

"That's it."

Donnie frowned to himself. That wasn't true, he knew, but he just said, "Okay."

Donnie was about to ask Leo something else when Mikey entered the room. "Leo, Space Heroes is on!" Leo left the room along with Mikey, leaving Donnie alone.

Donnie let out an irritated sigh. _What_ was wrong with Leo?

* * *

><p>Raph and Donnie were in the living room. Space Heroes was on, but they weren't watching. They were studying Leo, who didn't really seem to be paying attention to the show.<p>

"Leo, want some popcorn?" Mikey asked.

Leo blinked and looked at the tub of popcorn Mikey was offering. "Uh... no thanks. I just... um... need some water." He stood up and walked towards the kitchen, only to be stopped by Raph.

"You aren't going anywhere," Raph growled, holding Leo's arm tightly.

Leo glared. "Why?"

"'Cause you aren't telling us what's wrong!"

"Nothing's wrong." Leo tried to struggled out of Raph's grasp, but Raph only held on tighter.

"Something_ is_ wrong. Nothing can stop you from watching Space Heroes, especially not thirst," Donnie pointed out.

"So what? I just got really thirsty!"

"Tell us what's wrong!" Raph said, keeping his grip firm.

"_Let me go_!" With a strength no one ever knew he had, Leo pulled out of Raph's grasp and kicked him away. Leo unsheathed his swords and smirked evilly at Donnie.

Donnie gasped as Leo swiped his sword at him. Having no other choice, he and Raph took out their own weapons and blocked Leo's blows.

"Leo, please stop! We don't want to hurt you!" Donnie pleaded. But Leo didn't seem to have heard him. He just brought his sword down, barely missing Donnie's head.

Raph tried to help defend Donnie, but Leo simply kicked at his injured shoulder, making him fall down in pain. Donnie was on his own now.

Donnie spun his bo staff expertly. Leo was unfazed by this and continued to try to hit Donnie with his swords.

"Leo, _please_!" Donnie begged. He looked up into Leo's eyes and gasped.

Leo's eyes were _red_.

Donnie thought he saw a flicker of blue, but then Leo brought his sword down. With only seconds to react, Donnie brought his bo staff up. Leo's katana cut the 'stick' in half.

"Not _again_!" Donnie said, annoyed. This was probably the fiftieth time his weapon had broken.

Leo took the chance to charge at Donnie. The purple masked turtle noticed this too late. The next thing he knew, Leo was pinning him down, his sword right next to his neck.

"Leo," Donnie whispered, "you don't want to do this."

The katana moved closer to Donnie's neck.

Donnie's heart was beating fast. He thought fast. "Leo, I... I... I love you."

Leo blinked, and to Donnie's joy, his eyes were their normal shade of sapphire blue. "Donnie?" Leo gasped as he saw his katana was next to his brother's neck. Leo quickly stood up, sheathed his weapons, and helped Donnie up.

"Leo... what's wrong?" Donnie asked quietly.

Leo didn't seem to hear that and just whispered, "It's him."

"Who?" Donnie asked, confused.

"My dark side."


	7. Secrets Revealed

**A/N: I know I haven't updated in a while... sorry! **

**You might want to reread some of the older chapters to refresh your mind.**

**Also, this chapter is really important to the story, so don't skip anything!**

* * *

><p>It was a mistake.<p>

Leo hadn't meant to say that.

But they were his _brothers_. They had a right to know what was happening.

He tried to say more, but no sound came out of his mouth, thanks to Dark Leo. Before he knew it, his legs moved and forced him to sprint out of the lair like they had a mind of their own.

His legs brought him out of the sewer and up to the surface, making him leap over buildings until he reached one.

Leo recognized the building. It was the Foot Headquarters.

Suddenly, a figure materialized next to him. It was a turtle, a _black_ turtle, with red, glowing eyes.

_Dark Leo_.

_"Nice to see you again," he greeted._

Leo scowled and looked away.

_"You're wondering why I'm here, aren't you?"_

Leo refused to say anything.

_"Well, I'm here to tell you why."_

Leo looked up and glared at his dark side. "Then tell me why."

_"Well, back in Japan, when you were a normal, not mutated, baby turtle, the Shredder bought you and kept you like a pet. He brought you everywhere, and you liked it. You enjoyed his company,"_ Dark Leo said.

Leo said nothing.

Dark Leo continued. _"He used to give you orders and you would listen. One day, after killed Tang Shen and almost got rid of Hamato Yoshi, he decided to go to New York City. He lost you there. Some people found you and brought you to a pet store. Hamato Yoshi bought you along with three more turtles, and you know the rest."_

"...So how does _that_ make me have a dark side?" Leo asked.

_"Because you have a connection with the Shredder, making you have a dark side, which is me. He gives me orders through meditation,"_ Dark Leo said.

"_The Shredder_ meditates?"

_"Yeah."_

Leo thought about this for a while. "But how does that explain how I heard him telling me he wants revenge?"

_"Oh, that's because he sometimes controls you, too,"_ Dark Leo said.

"_What_?!"

_"Sometimes he goes into the deepest state of meditation and controls you,"_ Dark Leo said. He sounded like it was unimportant.

"...No," Leo said. If the Shredder controlled him, he would definitely harm his brothers. He would make Leo kill them.

And the fear that was worse than failure to Leo would to be the cause of his brother's deaths.

_No. No._

Dark Leo suddenly disappeared. Confused, Leo turned around.

"Hey, bro," Mikey greeted from behind him.

"Mikey, how long were you here?" Leo asked.

"I just got here," Mikey said. "Donnie stayed home to patch up Raph and I went looking for you."

Leo struggled to remember what had happened. "Patch up Raph?"

"Uh, yeah. When you kicked him, you opened his stitches, and he started bleeding..." Mikey trailed off.

Leo was silent for a few moments, but then he said, "Come on, let's go."

* * *

><p>"Guys, it's time for dinner! We're having pizza!" Mikey called from the kitchen.<p>

"We're coming," Donnie said from his lab.

Sure enough, Donnie, Raph, and Leo went into the kitchen and took their places. Mikey gobbled up his pizza and reached for another slice, then another. Then he noticed that the others had barely eaten; the only turtles who had even bothered to touch their pizza were Raph and Donnie. Leo was just staring at his pizza slice.

"I think I'll go to bed now," Mikey said, forcing a yawn.

Donnie pushed his plate away. "I'm not hungry. I'm going to bed, too." He got up and went to his room, leaving his unfinished food on the table.

"Leo, what was that about your dark side?" Raph asked, daring Leo to dodge the question.

Leo tried to answer, but nothing came out.

"They're real, aren't they? Never thought they were, but it would explain what's happening to you."

Still nothing came out.

"You can tell me. You trust me, don't you?"

"Yeah..." Leo finally said.

"Then why don't you tell me?"

Leo couldn't answer that. His mouth wouldn't work.

Raph sighed. "Don't you remember the times when we were little and we used to tell each other _everything_?"

Leo nodded. He remembered those times clearly when he and Raph were best friends, maybe even more than that. They used to tell each other everything they knew, secret or not. But then, when Leo became the leader, everything changed. They got into fights more often and changed from best friends to enemies. Of course, they were still friends, but they didn't do the same things they used to do anymore.

"Well, then, tell me! You need to tell someone! You need_ help_!"

"...It's much too complicated, Raphael."

Leo inwardly gasped. He hadn't meant to say that. And it had come out sharp and cold.

It was the doing of Dark Leo.

Raph, not knowing that Leo's dark side made him say that, shot back. "_Everything_ is complicated, Leonardo."

Leo stared at Raph. No one other than Master Splinter called him by his full name.

Leo got up. "I'm going to bed. 'Night."

"'Night," Raph said gruffly, watching his older brother go to his room.

None of them noticed Mikey scurrying up to his own room. He had been eavesdropping on the whole conversation.

Leo slipped into his bed and stared at the ceiling. He was tired, but he had a feeling something was going to happen.

Suddenly, Dark Leo appeared right next to him. _"Hello."_

Leo glared and turned away.

_"I'm getting stronger. I can control your actions _and_ what you say or don't say now."_

When Leo didn't say anything, Dark Leo continued. _"Soon, you'll be entirely evil. You only have about forty percent of your good side left in you, you know."_

"...No," Leo finally said.

_"I'll hurt your brothers. Oh wait no, I'll make _you_ hurt your brothers!"_

"No!"

_"Well, I won't on one condition."_

"What?"

_"If you promise not to say anything about me to anyone, I won't do that."_

Leo knew that making promises to an enemy was never a good choice. But he had no choice.

"...I promise."

_"You have to promise you won't tell anyone about this promise, either."_

"...I promise."

_"Good. Now you must keep your promises, or your brothers will get hurt,"_ Dark Leo said. Then he disappeared.

Leo, exhausted from the day's events, immediately fell into a dreamless sleep, unaware of Raph standing on the other side of the door to his room.

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><p><strong>AN: Well, I hope this chapter was good enough for you. Oh, and I promise it won't take fifteen days for the next update!**

**Please review, follow, and favorite. ;)**


	8. The Second Invasion

**A/N: Well, I kept my promise; it didn't take 15 days for me to update!**

**I don't own TMNT.**

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><p>He was in the darkness again.<p>

That same empty feeling enveloped him.

_I'm in a dream again,_ he realized.

But if he was in a dream, wouldn't there be someone or something there, too?

Right now, it was just him and the darkness. He could feel it and see it again, just like last time.

He tried to move, but the darkness seemed to hold him down, preventing him from moving even a single centimeter.

Sighing, he stayed still, waiting for something to happen.

He waited for a minute. Nothing.

He waited for half an hour. Nothing.

He waited for an hour. Nothing.

And then, just when he thought nothing was going to happen, someone materialized right in front of him.

He gasped. "_Master Splinter_?"

Master Splinter, however, wasn't looking at him. He was looking in his direction, but not at _him_.

"Never trust the enemy, my son," Splinter said, and then he disappeared.

Leonardo woke up with a start. His sensei's words were echoing in his head.

_Never trust the enemy, my son._

What did it mean?

Did it mean not to trust his dark side?

Leo always knew that trusting the enemy was never a good idea. Mikey had learned that the hard way, and ever since, the turtles abstained from even thinking about trusting the enemy.

Leo sighed. He wasn't getting any answers from this. _Maybe meditation will help,_ he thought. He lit a candle and sat in the lotus position on the floor, trying to clear his head.

He was later jolted awake by the door of his room being opened loud and violently. He looked up and saw Donnie with a worried expression on his face.

"Leo, I was looking at the security cameras and it showed lots of Kraang heading towards the lair! I think they remembered our location from the last invasion, and they know we're alive because they saw us when we went to unmutate those Kraang zombies! They're going to attack us!" Donnie said, the words flowing hurriedly out of his mouth.

"Don't worry, Don, we'll get rid of them. Did you tell Raph and Mikey?" Leo asked.

"Yes," Donnie answered. "We have to go! The Kraang are going to be here any sec-"

There was a loud crash as the lair door fell down and the Kraang invaded the lair.

"-ond," Donnie finished. He and Leo grabbed their weapons and rushed out of the room.

The lair was filled with Kraang. Raph and Mikey were already fighting some of them, trying not to get hit by the lasers some other Kraang were shooting from laser guns.

"We need a plan!" Leo yelled over the Kraangs' voices.

Raph rolled his eyes as he stabbed a Kraang's robotic body with his sai. "Isn't that obvious, Fearless?"

Ignoring the comment, Leo said, "You guys stay here and fight. I'll lead the Kraang that are coming away. Then we'll meet up at April's."

Mikey looked up at the leader, his blue eyes filled with uncertainty and fear. "But that's what we did last time and-"

Leo tried to comfort the youngest turtle. "Mikey, it won't happen again." Ignoring Donnie's and Mikey's protests, he made his way to the exit, fighting some Kraang on the way. Right when he was about to go out of the lair, however, he was stopped by none other than Raphael.

"You aren't going, Leo. I am."

"I'm going, Raph. Every leader has to make sacrifices."

"You've made too many sacrifices already."

"It doesn't mean I can't make more."

Raph fixed his eyes onto Leo's, sending the blue masked turtle a murderous glare. "_You're_ staying. _I'm_ going."

Leo finally give in. "Fine! Go! See if I care!"

Raph looked at Leo right in the eye again. "I don't want you to go through that again," he said softly, in an almost kind manner. Then he left.

Leo stood their for a few moments. He couldn't believe he had just said that.

He couldn't believe that_ Raph_ had just said that. Mikey or Donnie might have said something like that, but Raph? Never.

Never before.

Leo turned back to the fight. He kicked and punched the Kraang, defeating all of them, but he was vaguely aware of that. His mind was elsewhere.

* * *

><p>"He's not answering!" Mikey cried. They had defeated the Kraang that had invaded the lair and escaped to April's apartment. Now they were waiting for Raph.<p>

"Don't worry, he's probably just fighting some Kraang right now and is too busy to answer," April said.

"But I called him five times! He should have answered by now!" Mikey said, obviously worried for Raph.

"You called him five times without pausing. Of course he didn't answer," Donnie said.

"But what if he comes crashing through the window just like Leo did?" Mikey asked worriedly.

At the mention of his name, Leo, who had been gazing out the window, turned his head and glared at Mikey. "He won't," Leo said sharply and looked out the window again.

Mikey cringed at the tone of Leo's tone, but didn't say anything. He just tried to call Raph again.

"I'm here!" Raph said, slipping inside the apartment from the window Leo wasn't at.

Mikey ran forward and threw his arms around Raph. "I missed you, bro!"

Donnie, too, was relieved, but Leo only glared at Raph. "Why were you late? You had them all worried," he said coldly.

"I ran into some Foot Bots but I'm okay," Raph said simply.

Leo didn't hear him. He was feeling the all too familiar pain which indicated that Dark Leo was taking over him.

Again.

His eyes turned red. He suddenly charged towards his brothers, his hands holding his swords tightly.

Donnie was the first to notice. "Guys, his dark side has him again!"

All the turtles quickly got their weapons and fought Leo, since they had no other choice.

"We have to try to get Leo back," Donnie said.

"How? The same way you did yesterday? That was from that stupid movie you and Mikey watched the other day!" Raph said.

"Well, yeah," Donnie said sheepishly. "It worked, though!"

Raph had a different idea. "Leo!" he tried. "Leonardo!"

Donnie caught on. "We're your brothers, Leo!

"Yeah! We don't want to fight you!" Mikey said.

There was a flicker of blue in Leo's eyes but it was quickly replaced by red.

"Fearless!" Raph tried again. "Fearless Leader!"

Relief flooded through the other turtles as Leo's eyes turned completely blue.

"Are you okay?" Raph asked.

Leo didn't answer. He was exhausted. Fighting his dark side became harder every day.

He knew he couldn't stay awake any longer.

A wave of dizziness passed over him and he fell backwards, unconscious.

* * *

><p><strong>AN: Well, I hoped you liked this chapter. **

**Remember to review, follow, and favorite! :)**


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